You're confusing pumped storage with river dams. The geography for pumped storage is abundant, river dams not so much.
>Battery storage is entirely speculative so far.
In 2012 maybe. These days grid level battery plants are deployed routinely.
>Whilst nuclear is a proven baseload source
At 5x the cost per kwh, according to lazard.
Baseload also means "requires peakers". That means gas or...batteries.
When french nuclear plants go down for maintenance the country chews through ungodly amounts of gas. Some of their plants have capacity factors of like ~80% - not much better than high performing wind farms.
Battery systems installed in the last 5 years in America are 15 times more powerful than all the fission reactors built in the same time. Meanwhile, US reactor capacity is now lower than it was in 1990. One of these power sources is "speculative" and the other is a rapidly-growing, practical and economical way to store and distribute energy.